JP2003001850A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a decrease in printing performance and nozzle clogging by reducing fluctuations in back pressure in a buffer tank 5 during printing operations. SOLUTION: A print head 2 and the buffer tank 5 are mounted on a carriage 4 so as to be made movable, and ink is supplied to an ink inflow cylinder 8 of the buffer tank 5 from a sub-tank 32 in a fixed position via flexible tubes 13 and 34. A midway part of a tubular tube body 15, whose one end is connected to an opened cylinder 9 communicating with a ceiling wall 7 (a pneumatic part) of the buffer tank 5, is extended in a horizontal direction orthogonal to a direction of movement of the carriage 4, and an isolation member 20, which serves as a liquid meniscus composed of a nonvolatile high-viscosity liquid (glycerin), is arranged movably in the midway part of the tube body 15. The fluctuations of the back pressure in the buffer tank 5, which are attendant upon the advance/retreat operations of the ink in the flexible tubes 13 and 34, are absorbed by movement of the isolation member 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a piezoelectric type ink jet recording apparatus having a print head for supplying ink from an ink tank for printing.

[0002]

2. Description of the Related Art Conventionally, in an ink jet recording apparatus for ejecting and recording an ink on a recording medium based on an input signal, the ink is guided from an ink tank to a plurality of ejection channels of a print head through an ink flow path, It is known that an actuator such as a heating element or a piezoelectric element is selectively driven to eject ink from the tip (nozzle) of an ejection channel. In this type of ink jet recording apparatus, as disclosed in Japanese Patent Application Laid-Open No. 2000-190513, a small serial printer type apparatus has a print head and ink on a carriage that reciprocates with respect to a recording medium. Although there are those equipped with an ink cartridge as a supply source, the moment of inertia at the time of stopping and returning at the moving end of the carriage becomes large in correspondence with the weight of the ink cartridge and the ink liquid inside thereof. However, there is a problem that an extra resistance force is applied to the drive source of the carriage, and when the ink cartridge is downsized, the ink cartridge is frequently replaced due to the consumption of ink, and a large amount of continuous recording can be performed quickly. There was an inconvenience that I could not.

Therefore, as disclosed in JP-A-5-16382, a replaceable ink supply source such as an ink cartridge is arranged on the recording apparatus main body side, and a flexible tube is connected from the ink supply source. A configuration is known in which ink is supplied to a print head on a carriage via the ink.

As disclosed in this publication, the sub-tank which is detachably connected to the print head is mounted on the carriage together with the print head and integrally scans and moves. Instead of completely filling the ink, it is used in the state where a predetermined amount of air is stored. Due to the presence of the air portion, the impact force caused by the movement / stop of the print head is mitigated, and the ink prevents the pressure fluctuation in the ejection channel of the print head to maintain uniform ejection performance.

[0005]

However, when the print head is started and stopped frequently and rapidly in response to the recent demand for higher printing speed, the air reservoir portion of the sub-tank is hermetically sealed. In addition, due to the inertial flow of ink in the flexible tube from the ink supply source to the sub tank of the print head, the pressure fluctuation in the sub tank becomes too large. As a result, when the pressure in the sub-tank is too large on the positive pressure side, it exceeds the meniscus pressure resistance at the nozzle portion, ink leaks from the nozzle surface and carelessly stains the recording medium, or conversely, in the sub-tank. If the pressure is too large on the negative pressure side, the meniscus pressure resistance of the ink in the nozzle portion is broken, and during printing, the atmosphere enters the print head from the nozzle and accumulates as bubbles in the ejection channel, causing ejection failure. There was a problem that frequently occurs.

The present invention has been made to solve such a problem, and a liquid state is formed in a pipe body communicating with an air portion of a buffer tank connected to a print head that moves and stops integrally with a carriage. By providing the pressure fluctuation absorbing means configured so that the separating member of can be moved,
It is a technical object to provide an ink jet recording apparatus in which the pressure fluctuation does not increase and ink leakage and ejection failure do not occur.

[0007]

In order to achieve this technical object, an ink jet recording apparatus according to a first aspect of the present invention is an ink tank which is open to the atmosphere for storing ink, and a print head having a plurality of ejection channels. And a buffer tank connected to the print head, and an ink supply path for supplying ink from the ink tank, in an inkjet recording apparatus, a tube body having one end communicating with an air portion in the buffer tank, and the tube. The pressure fluctuation absorbing means is composed of a liquid separating member that is movably arranged in the middle of the body.

According to a second aspect of the invention, in the ink jet recording apparatus according to the first aspect, the separating member is made of a non-volatile high viscosity liquid.

The invention described in claim 3 is the same as claim 1
Alternatively, in the ink jet recording apparatus according to claim 2, the height position of the ink tank with respect to the print head is set so that a back pressure that prevents ink droplets from leaking from nozzles in the print head is applied to the buffer tank. It was done.

Further, according to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects, one end of the pipe body is opened to a ceiling surface of the buffer tank, and the pipe is formed. The body is extended in a direction intersecting the moving direction of the print head.

According to a fifth aspect of the present invention, in the ink jet recording apparatus according to any of the first to fourth aspects, the ink tank temporarily stores ink supplied from an ink supply source such as an ink cartridge. It is a sub tank.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of an ink jet recording apparatus of the present invention, FIG. 2 is a sectional view of an essential part of a second embodiment, and FIG. 3 is a sectional view of an essential part of a third embodiment. A print head 2 having a plurality of ejection channels (not shown) is arranged on the lower side of the head unit 1, and a manifold chamber 3a communicating with all the ejection channels is provided on the upper side.
A manifold body 3 having the above is arranged, and both are bonded and fixed to form a unit.

The head unit 1 is fixedly mounted on the lower surface side of the carriage 4 with an adhesive or the like, and the buffer tank 5 is removably fixed to the upper surface side thereof with mounting screws 6. Ink cartridge 3 as an ink supply source
0 is connected to the bottom surface of the sub tank 32 through a flexible tube 31 made of synthetic resin, and the ink in the ink cartridge 30 is replenished and supplied to the sub tank 32 by driving the first pump 33 for supplying ink. . Sub tank 3
The other end of the flexible tube 34 as an ink supply flow path connected to the bottom surface of the connection member 2 is connected to the connection member 14 fixedly provided on the side of the carriage 4 and connected to the connection member 14 for relaying. The other end of the flexible tube 13 made of synthetic resin is connected to the ink inlet 8 of the buffer tank 5.
The sub tank 32 is provided with an atmosphere opening portion 32a on its upper surface,
A second pump 35 for supplying ink is provided in the middle of the flexible tube 13 made of synthetic resin for relay.

In the present embodiment, the ink cartridge 30 and the sub-tank 32 are arranged at predetermined positions on the main body side of the recording apparatus, and the carriage 4 is mounted via a timing belt, a step motor or the like (not shown). It is configured to be capable of reciprocating in a direction orthogonal to the paper surface of FIG. Further, the carriage 4 is reciprocating along a surface of a sheet (not shown) as a recording medium and along a carriage moving direction orthogonal to the sheet feeding direction,
At one end of the carriage 4 in the moving direction, a suction cap 37 for suction purging is arranged so as to face the print head 2, and during suction purging, the suction cap 37 is on the front surface (lower surface) of the print head 2. ) Is closely contacted so as to cover the nozzle part, and the suction pipe 38 and the suction pump 39
It is discharged to the drain tank 40 via.

Next, the print head 2 will be described.
Although it is not shown because it has a known structure as disclosed in Japanese Patent Laid-Open No. 2000-103084 and the like, it has a structure in which two actuator substrates each having a plurality of ejection channels on both sides of the substrate are adhered to each other, and the lower surface thereof is Nozzles communicating with each injection channel are opened in two rows.
On the upper surface of each actuator substrate, a manifold body 3 is provided in which a manifold chamber 3a is arranged so as to communicate with each of the injection channels. The introduction pipes 12 and 12 connected to the upper surfaces of the manifold chambers 3a and 3a (only one of which is shown in FIG. 1) are connected to ink outlets 10 opened in a bottom plate 5a of a buffer tank 5 which will be described later via seal pipes 18 and 18. It is connected. As a configuration for ejecting the ink in each ejection channel, it is preferable that the side wall of the actuator substrate near the ejection channel is made of a piezoelectric material and the ink is ejected by the deformation of the piezoelectric material.

An ink inflow cylinder 8 hangs down from the ceiling wall 7 of the buffer tank 5 and opens near the bottom plate 5a of the buffer tank 5. The upper end of the ink inflow cylinder 8 projects upward from the ceiling wall 7. Further, an opening cylinder 9 is formed at a portion near the one side of the ceiling wall 7, and an inner surface (ceiling surface) 7a of the ceiling wall 7 is lower as a whole as one can see from FIG. It is formed on an inclined surface having an inclination angle θ with respect to the horizontal plane so as to be located at a high position on the cylinder 9 side. This tilt angle θ is approximately 5 degrees as an allowable tilt angle (device allowable tilt angle) when a main body (not shown) of a printer equipped with the ink jet recording apparatus of the present embodiment is placed on a mounting surface such as a table. The added value is about 5 to 15 degrees in the embodiment, and more preferably about 10 degrees.

Each of the pair of ink outlets 10 and 10 projecting downward from the bottom plate 5a of the buffer tank 5 has an upper surface side (inside the buffer tank 5) of 5 μm or more.
A filter 11 having a mesh size of about 10 μm is stretched so that bubbles and foreign matters in the ink can be captured.

The liquid level of the ink in the sub tank 32, which is open to the atmosphere, is appropriately higher than the height position of the nozzle surface of the print head 2 (the lower surface of the print head) H2 (in the embodiment, a water column (water head)). 100 mm) lower, so that the ink pressure on the nozzle surface of the print head 2 is set to a negative pressure head (the water column (head) 100 mm lower) than the atmosphere.

In the opening cylinder 9 communicating with the upper side near the air portion (ceiling wall 7) in the buffer tank 5, in the embodiment, a tubular body as a part of the pressure fluctuation absorbing means made of a synthetic resin tube or the like is used. Connect one end of 15. A liquid separating member 20 is movably inserted in the middle of the tube 15. In the embodiment, the isolation member 20 as a part of the pressure fluctuation absorbing means is preferably a material which does not corrode the pipe body 15 and does not freeze or evaporate due to room temperature and climatic heat, and is a non-volatile high viscosity liquid. For example, glycerin or the like is used. With such a high-viscosity liquid, when the tube body 15 is set in a substantially horizontal shape, the liquid meniscus pressure resistance is high,
The air chamber portion of the buffer tank 5 of the pipe body 15 and the chamber 15a on the front end side of the pipe body 15 can be reliably shut off.

Most of the pipe body 15 is arranged in a substantially horizontal state, and the pipe body 15 is extended in a direction intersecting the moving direction of the carriage 4 (direction orthogonal to each other). As a result, the isolation member 20 as a damper (buffer) inside the pipe body 15 does not move in the axial direction of the pipe body 15 due to the inertial force accompanying the movement of the carriage.

In the first embodiment shown in FIG. 1, the tip (free end) of the tube body 15 is sealed with the plug 21 so that the pressure in the chamber 15a on the tip side becomes equal to the back pressure P2. By doing so, the isolating member 20 is stationary at a predetermined position inside the tubular body 15 in the stationary initial state.

The flexible tube 13 and the tubular body 1
5 is protected by a protective cover body 4a attached to the carriage 4.

In this configuration, for example, the print head 2
Meniscus pressure resistance P1 of the nozzle is minus 350 mm (water column), the back pressure P2 given to the nozzle is minus 100 mm
(Water column), the meniscus pressure resistance P3 of the isolation member 20 ±
100 mm (water column), the maximum value P4 of pressure fluctuation received from the flexible tubes 13 and 34 due to the movement of the print head 2 is ± 200 mm (water column), and the meniscus pressure resistance P5 that the print head 2 can normally print is 0 mm to minus 200 mm (water column) (1). Initial state in which the print head 2 (carriage 4) is stationary ... The back pressure of P2 is applied to the nozzle (print head 2) from the buffer tank 5 side, which is higher than the meniscus pressure resistance P1 of the nozzle (P1 <P2). The destruction of the meniscus at the nozzle does not occur. Further, since the meniscus pressure resistance P3 (absolute value) of the separating member 20 is larger than the back pressure P2, the separating member 20 does not move. (2). Tubes 13 and 34 due to movement of the carriage 4
When the back pressure P2 is increased due to the pressure fluctuation of the ink in the inside (2-1). Pressure fluctuation received from the tubes 13 and 34 + ΔP4
Up to +100 mm (water column), | ΔP4 | <| P3
| (= 100 mm), the separating member 20 does not move.
Since P2 + ΔP4> P1, the meniscus of the nozzle is not destroyed, and therefore the atmosphere is not sucked into the print head 2 from the nozzle surface. Also, P2 + ΔP4 ≦ P5 (maximum value), and the back pressure in the buffer tank 5 fluctuates (increases).
Also, it does not affect the printing performance of the print head 1.

(2-2). When pressure fluctuation ΔP4 received from tubes 13 and 34 exceeds +100 mm (water column), | ΔP
4 |> | P3 | (= 100 mm), so the isolation member 20
Moves back and forth along the longitudinal direction of the tubular body 15, and ΔP4 =
It stops at the position of P3. That is, tubes 13 and 3
When the ink in 4 moves forward to approach the ink inflow cylinder 8 of the buffer tank 5 and the back pressure p2 in the buffer tank 5 increases, the separating member 20 moves away from the opening cylinder 9 in the middle of the tubular body 15. It will retreat to and maintain the pressure balance.

Further, since P2 + ΔP4> P1, the meniscus of the nozzle is not destroyed, and therefore the atmosphere is not sucked into the print head 2 from the nozzle surface.

Further, P2 + ΔP4 = P5 (maximum value), and fluctuation (increase) in back pressure in the buffer tank 5 does not affect the printing performance of the print head 1. (3). Tubes 13 and 34 due to movement of the carriage 4
When the back pressure P2 is reduced due to the pressure fluctuation of the ink inside the tube (3-1). Pressure fluctuation received from the tubes 13 and 34 (-ΔP
When 4) is back pressure P2 (= -100mm (water column)),
Since | ΔP4 | <| P3 | (= 100 mm), the separating member 20 does not move. Also, because P2 + ΔP4> P1,
The meniscus of the nozzle is not destroyed and therefore the atmosphere is not sucked into the print head 2 from the nozzle surface. Further, P2 + ΔP4 ≦ P5 (minimum value), and the fluctuation (reduction) of the back pressure in the buffer tank 5 does not affect the printing performance of the print head 1.

(3-2). When the pressure fluctuation ΔP4 received from the tubes 13 and 34 exceeds the back pressure P2 (= -100 mm (water column)), | ΔP4 |> | P3 | (= 100 mm),
The separating member 20 moves back and forth along the longitudinal direction of the tubular body 15 and stops at a position where ΔP4 = P3. That is, the ink in the tubes 13 and 34 retreats away from the ink inflow cylinder 8 of the buffer tank 5 and moves back to the buffer tank 5.
When the back pressure p2 in the inside decreases, the isolation member 20 moves the tube 1
The pressure balance is maintained by advancing in a direction approaching the opening tube 9 in the middle of 5.

Since P2 + ΔP4> P1, the meniscus of the nozzle is not destroyed, and therefore the atmosphere is not sucked into the print head 2 from the nozzle surface. Furthermore, P
2 + ΔP4 = P5 (minimum value), and the buffer tank 5
The fluctuation (reduction) in the back pressure does not affect the printing performance of the print head 1.

FIG. 2 shows an essential part of the second embodiment of the pressure fluctuation absorbing means, and an opening provided in the ceiling wall 7 so that one end of the tubular body 15 made of synthetic resin or the like communicates with the air portion of the buffer tank 5. It is connected to the cylinder 9 and extends substantially horizontally in a direction intersecting the moving direction of the carriage 4. Then, a middle portion of the tubular body 15 is bent downward to form a U-shaped portion 15b, and the separating member 20 made of the same non-volatile high-viscosity liquid as described above extends to the bottom of the U-shaped portion 15b and its vicinity. Is movably arranged. The tip side 15a of the tubular body 15 is open to the atmosphere. According to this embodiment, due to the weight of the separating member 20 in the U-shaped portion 15b,
As long as the pressure fluctuation is not too large, the isolation member 20
It is considered that there is no leakage from the tip end portion 15a of the tubular body 15 to the outside beyond the character-shaped portion 15b.

FIG. 3 shows a third embodiment of the pressure fluctuation absorbing means. In this embodiment, an appropriate amount of the liquid separating member 20 is previously put into the pipe body 15 having the tip side (bottom part) 15a sealed, and then the base end opening of the pipe body 15 is opened in the buffer tank 5. Connect to the tube 9. This tube 15
Extend in a direction intersecting (substantially orthogonal to) the moving direction of the carriage 4. After that, when a back pressure P2 lower than atmospheric pressure is applied to the buffer tank 5, the pressure on the tip side 15a becomes a vacuum state, and the isolation member 20 is always kept on the tip side 15a.
Even if the back pressure in the buffer tank 5 decreases, the amount of movement of the isolation member 20 toward the opening tube 9 is small and the buffer tank 5 is carelessly moved.
The isolation member 20 does not enter inside.

The pipe body 15 may be arranged substantially horizontally with respect to the horizontal plane, but in the first to third embodiments as well, the tip end side 15a of the pipe body 15 is slightly lower. You may incline.

By moving the carriage 4 (print head 2) as described above, the ink in the tubes 13 and 34 for supplying the ink from the sub tank 32 at the fixed position to the buffer tank 5 that moves is inertial force. Even if the back pressure in the buffer tank 5 fluctuates oscillatingly,
By the pipe body 15 communicating with the air portion of the buffer tank 5 and the separating member 20 made of a non-volatile high-viscosity liquid as a liquid meniscus movably arranged in the middle thereof,
As a result of maintaining the back pressure in the buffer tank 5 substantially constant,
Even if the back pressure in the buffer tank 5 fluctuates over a wide range from high frequency to low frequency, it is possible to eliminate the inconveniences such as deterioration of the printing performance of the print head 2 and suction of bubbles from the nozzles.

Instead of the above-mentioned configuration, the print head 2 is one that locally boils and ejects ink by a known heating portion, and electro-mechanical elements such as piezoelectric elements in ejection channels arranged in a plane. A device in which the displacement conversion means are opposed to each other can be applied. Also in these cases, the ink outlet of the buffer tank is connected to the manifold chamber that distributes the ink to the plurality of ejection channels. The buffer tank may be directly connected to the print head without the manifold body 3.

Further, the ink supply tank disposed on the main body side (fixed side) of the recording apparatus may be an ink cartridge by omitting the sub tank 32.

[0035]

As described above, claim 1
The ink jet recording apparatus according to the invention described in (1), an ink that supplies ink from the ink tank to an atmosphere open type ink tank that stores ink, a print head having a plurality of ejection channels, and a buffer tank connected to the print head. In an ink jet recording apparatus provided with a supply path, a pressure fluctuation absorption composed of a tube body having one end communicating with an air part in the buffer tank, and a liquid separating member movably arranged in a middle part of the tube body. It is equipped with means.

Therefore, as the print head moves, the ink in the ink supply path for supplying the ink from the ink tank at the fixed position to the moving buffer tank moves back and forth due to inertial force, and the back pressure in the buffer tank increases. Even if the vibration fluctuates, the inside of the buffer tank is separated by the pipe body communicating with the air portion of the buffer tank and the isolation member made of a non-volatile high-viscosity liquid as a liquid meniscus movably arranged midway. As a result of being able to maintain the back pressure of the print tank substantially constant, the print performance of the print head deteriorates even if the back pressure in the buffer tank fluctuates over a wide range from high frequency to low frequency, and air bubbles from the nozzle to the ejection channel The effect that the nozzle is not clogged due to suction is obtained.

According to a second aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the separating member is made of a non-volatile high viscosity liquid. By using a non-volatile, high-viscosity liquid as the isolation member in this way, it is possible to use the liquid meniscus to quickly follow minute changes in back pressure and move within the pipe body, and the back pressure in the buffer tank is substantially constant. The effect of being able to easily hold the structure is obtained.

The invention described in claim 3 is the same as claim 1
Alternatively, in the ink jet recording apparatus according to claim 2, the height position of the ink tank with respect to the print head is set so that a back pressure that prevents ink droplets from leaking from nozzles in the print head is applied to the buffer tank. Therefore, it is possible to easily prevent the ink from leaking from the nozzles of the print head simply by setting the positions where the ink tanks are arranged as described above.

Further, the invention according to claim 4 is the ink jet recording apparatus according to any one of claims 1 to 3, wherein one end of the pipe body is opened to the ceiling surface of the buffer tank, Since the body is extended in the direction that intersects the direction of movement of the print head, the isolating member inside the tube does not move due to the inertial force caused by the movement of the print head, which affects the fluctuation of back pressure in the buffer tank. Does not reach. Further, by making the middle part of the extension substantially horizontal, it is possible to provide a compact ink jet recording apparatus without being bulky even if the tube body is lengthened.

According to a fifth aspect of the present invention, in the ink jet recording apparatus according to any of the first to fourth aspects, the ink tank temporarily stores ink supplied from an ink supply source such as an ink cartridge. Since it is a sub-tank,
Even when the ink cartridge is replaced, since a predetermined amount of ink is stored in the sub tank, the back pressure applied to the buffer tank can be made substantially constant, and the ink does not accidentally leak from the nozzle of the print head. Produce an effect.

[Brief description of drawings]

FIG. 1 is a diagram of an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of an essential part of a second embodiment of a pressure fluctuation absorbing means.

FIG. 3 is a sectional view of an essential part of a third embodiment of a pressure fluctuation absorbing means.

[Explanation of symbols]

2 print head 4 carriage 5 buffer tanks 5a bottom plate 7 ceiling wall 8 ink inflow cylinder 9 open tube 10 Ink outlet 11 filters 13 Flexible tube 14 Connection member 15 Tubular body as part of pressure fluctuation absorbing means 20 Isolation member as part of pressure fluctuation absorbing means 30 ink cartridges 31 Flexible tube 32 sub tank 33 First pump 34 Flexible tube

Claims (5)

[Claims] 1. An atmosphere open type ink tank for storing ink, a print head having a plurality of ejection channels, and a buffer tank connected to the print head, and an ink supply path for supplying ink from the ink tank. In the ink jet recording apparatus, a pressure fluctuation absorbing means including a tube body having one end communicating with the air portion in the buffer tank and a liquid separating member movably arranged in the middle of the tube body is provided. An inkjet recording device characterized by the above. 2. The ink jet recording apparatus according to claim 1, wherein the separating member is made of a non-volatile high viscosity liquid. 3. A height position of the ink tank with respect to the print head is set so that a back pressure that prevents ink droplets from leaking from a nozzle of the print head is applied to the buffer tank. The inkjet recording device according to claim 1 or 2. 4. The pipe body according to claim 1, wherein one end of the pipe body is opened to a ceiling surface of the buffer tank, and the pipe body is extended in a direction intersecting a moving direction of the print head. The inkjet recording device according to any one of 1. 5. The ink jet recording apparatus according to claim 1, wherein the ink tank is a sub tank that temporarily stores ink supplied from an ink supply source such as an ink cartridge.